1. Field of the Invention
The present invention relates to exposure apparatuses, exposure methods and device manufacturing methods, and more particularly to an exposure apparatus and an exposure method used in a lithography process to manufacture electron devices (microdevices), and a device manufacturing method using the exposure apparatus or the exposure method.
2. Description of the Background Art
Conventionally, in a lithography process to manufacture electron devices (microdevices) such as a semiconductor device (an integrated circuit and the like), a liquid crystal display device and the like, a projection exposure apparatus employing a step-and-repeat method (a so-called stepper), or a projection exposure apparatus employing a step-and-scan method (so-called scanning stepper (also called a scanner)) is mainly used.
In this type of exposure apparatus, in general, a position of a wafer stage which moves two-dimensionally while holding a substrate such as a wafer or a glass plate or the like (hereinafter collectively called a wafer) on which a pattern is transferred (or formed) was measured, using a laser interferometer. However, due to finer patterns accompanying higher integration of semiconductor devices in recent years, requirements for position control performance of a wafer stage with higher accuracy have increased, and as a consequence, it has become difficult to ignore short-term variation of measurement values caused by air fluctuation which occurs due to the influence of temperature change and/or temperature gradient of the atmosphere on the beam path of a laser interferometer.
To improve such inconveniences, various proposals have been made of inventions related to exposure apparatuses that employ an encoder having a measurement resolution of the same level as or a higher level than a laser interferometer, as a position measurement device of a wafer stage (for example, refer to U.S. Patent Application Publication No. 2008/0088843). However, in the liquid immersion exposure apparatus disclosed in U.S. Patent Application Publication No. 2008/0088843 and the like, for example, the wafer stage (gratings provided on the upper surface of the wafer stage) may be deformed influenced by heat of vaporization and the like due to the liquid evaporating, and there still was room for improvement.
As an exposure apparatus to improve such inconveniences, an exposure apparatus has been known in which an exposure station where exposure of a wafer is performed and a measurement station where measurement operations such as wafer alignment are performed are each equipped with an encoder system which irradiates a measurement beam on a grating provided on a rear surface of a table that holds a wafer, from a head section provided at the tip of a measurement arm made up of a cantilever for example, refer to U.S. Patent Application Publication No. 2010/0296070).
However, in the exposure apparatus disclosed in U.S. Patent Application Publication No. 2010/0296070, a structure is employed in which, for example, a fine movement stage (wafer table) that holds a wafer is exchanged between two coarse movement stages via an intermediate member (for example, a center table, a relay stage, or the like). Therefore, there is a risk that such wafer exchange causes decrease in throughput of the apparatus. The wafer size is gradually increasing, and in the impending era of a 450 mm-wafer with a diameter of 450 mm, it is expected that further improvement in throughput is required, and accordingly it becomes difficult to cope with such requirement with the table exchange method as described above.